In a universal mobile telecommunication system (UMTS) which is an asynchronous mobile communication system, a transport channel provides a path for data transmission between a physical layer and a medium access control (MAC) layer. Unlike a logical channel, various kinds of transport channels can be used in accordance with occurrence characteristics of data which are transmitted. The transport channel can be divided into two types of a dedicated channel and a common channel. The dedicated channel means a channel used dedicatedly by a specific user equipment. The common transport channel is a channel that can be used commonly by a plurality of user equipments, and its examples include a random access channel (RACH), a forward access channel (FACH), a broadcast channel (BCH), a paging channel (PCH), a high speed downlink shared channel (HS-DSCH), a common packet channel (CPCH), and an uplink shared channel (USCH).
Among the aforementioned common transport channels, examples of channels used for downlink data transmission include FACH and HS-DSCH. Generally, the FACH is a downlink common channel used when a small number of data are transmitted to a user equipment. The HS-DSCH is a downlink common transport channel used for high speed data transmission in a high speed downlink packet access (HSDPA) system. On the HS-DSCH, a plurality of user equipments share radio resources by using a plurality of common channelization codes. Each of the user equipments can be allocated with a plurality of channelization codes within a single transmission time interval (TTS) in accordance with its capacity, and data for the plurality of user equipments can be transmitted by code multiplexing within a single HS-DSCH TTI.
The FACH can be mapped with a secondary common control physical channel (S-CCPCH) which is a physical channel, and then can downwardly transmit data dedicated for user equipment or common data. The S-CCPCH includes a transport format combination indicator (TFCI) field, a data field, and a pilot field. The TFCI field notifies a transport format of data transmitted to the data field. At this time, a radio network controller (RNC) of a network is in charge of scheduling of the FACH, and Node B serves to transmit FACH data in a wireless manner through the S-CCPCH in accordance with scheduling of RNC.